Sucker-rod pumping is a long established method for artificially lifting crude petroleum from an oil well. The components of a sucker-rod pumping system are immediately recognizable world-wide, especially the horse head and walking beam that commonly form the above-ground components of the subsurface pump. The above-ground components normally include a prime mover for providing driving power to the system, including gasoline and diesel engines and electric motors; a gear reducer for obtaining the necessary torque and pumping speed; a mechanical linkage for converting rotational motion to reciprocating motion, which includes the walking beam; a polished rod connecting the walking beam to the sucker-rod string; and a well-head assembly, sometimes referred to as a “Christmas tree,” which seals on the polished rod to keep fluids within the well and includes a pumping tee for removing oil to flow lines for storage and processing. Below ground, the downhole equipment may include a well hole casing; tubing within the casing and through which the oil is withdrawn; a rod string centrally located within the downhole tubing and composed of sections of sucker rod coupled to provide the necessary mechanical link between the polished rod and the subsurface pump; a pump plunger comprising a traveling ball valve and connected directly to the rod string to lift the liquid in the tubing; and a pump barrel, which is the stationary cylinder of the subsurface pump and contains a standing ball valve for suction of liquid into the barrel during the upstroke.
Sucker-rod pump operations sometimes have used magnets, including rare earth magnets, to assist in overcoming or delaying the precipitation of solids that can preclude a well from flowing and producing. Exposure to a magnetic field can delay or preclude precipitation of paraffins, asphaltines, and the like solids from crude petroleum as it cools, which precipitation tends to cause friction losses that can place stress on the rod string components or shut the well down. Typically, these magnets have been axially magnetized along a longitudinal axis, and may include rectangular or cylindrical magnets, generally placed on the production tubing exterior surface to expose fluid in the tubing to a magnetic field. Some of the apparatus that have been proposed require extensive retrofitting and may not offer a practical solution given the demands of production in the oil field.
Magnets sometimes are placed above ground to reduce scale and solids precipitation in the oil lines. Magnets are also used in connection with a wide variety of fluids conditioning apparatus, including for exposing water, vegetable oils, and other fluids to a magnetic field, typically for the purpose of aligning polar substances within the fluid to preclude or reduce solids deposition or to retrieve metallic objects from the fluid. For example, magnets have been placed on the end of a rod string for collection and removal of metallic contaminants from an oil well, but these tools generally cannot be used for removal of oil from the well.
It would be desirable to develop more efficient and useful methods and apparatus for exposing fluids to magnetic fields, including devices that do not require extensive retrofitting of existing apparatus, can potentially expose the fluid to an increased intensity of magnetic field, and that do not interfere with the operation of existing apparatus.